Example 5 
Let \(\mathcal {A}=\lbrace p,p^{\prime }\rbrace \) , \(\mathcal {E}=\lbrace \mathbf {not}\,\lnot p\rbrace \) , \(\Pi =(\mathcal {A},\mathcal {E},\mathcal {R})\)  with
\(\mathcal {R}\)  containing only rule \(p^{\prime } \leftarrow \lnot \mathbf {not}\,\lnot p\) , a well-known
formulation of the closed world assumption proposed in
[1]}In fact, in [1]}, the author
proposes the rule \(\mathbf {\sim }\,p \leftarrow \lnot \mathbf {M} p\) , where \(\mathbf {\sim }\,\)  is a third
kind of negation, usually referred to as strong negation, not considered in
this paper. It can be simulated by replacing occurrences of \(\mathbf {\sim }\,p\)  by a
fresh atom \(p^{\prime }\)  and adding a constraint rule \(\leftarrow p, p^{\prime }\)  that excludes \(p\) 
and \(p^{\prime }\)  to hold simultaneously..
